The present invention relates to a treatment tool for an endoscope, which is provided with an end effector including a pair of manipulation members pivotably supported at the distal end of the treatment tool so as to operate like pincers.
Treatment tools for endoscopes having end effectors operating like pincers include a biopsy forceps, a grasping forceps, a hemosatic forceps, a pinching forceps, or the like.
FIG. 1 shows a distal end portion of a conventional treatment tool provided with an end effector that operates like pincers. The conventional treatment tool has a flexible sheath 1 and a supporting member 2 attached to the distal end of the sheath 1. The supporting member 2 is provided with a slit 3 having a constant width. A supporting shaft 5 is held at the distal end of the slit 3 so as to cross the slit 3 in the width direction thereof.
A pair of manipulation members 4 is pivotably mounted on the supporting shaft 5. The proximal end portions of the manipulation members 4 are connected to a pair of operation wires 6 which are passed through the sheath 1. The pair of operation wires is advanced/retracted along the sheath 1 to open and close the pair of manipulation members 4 like a pair of pincers.
The supporting shaft 5 is mounted to the supporting member 2 by inserting it into a pair of through holes 10 formed to the supporting member 2 on both sides of the slit 3. Since the head of the supporting shaft 5 is formed in a diameter larger that the remaining part thereof, the supporting shaft 5 does not pass through the through holes 10. After being inserted into the through holes 10, the supporting shaft 5 is secured to the supporting member 2 by swaging the tip end thereof.
The supporting shaft 5 arranged as above does not come off from the supporting member 2 even if a large force is exerted thereon in a direction from the head toward the tip end thereof since the large diameter head of the supporting shaft 5 cannot pass through the holes 10. On the contrary, since the swaged tip end of the supporting shaft 5 may be deformed relatively easily, the supporting member may drop out from the supporting member 2 if it is pulled or pushed in a direction from tip end toward the head thereof, resulting in disassembling of the tip end of the treatment tool.
In order to make the supporting member insulative, the supporting member 2 is often made of non-metallic material. In such a case, the tip end of the supporting shaft 5 cannot be swaged with a large force since it may break the supporting member 2 having lower mechanical strength compared to those made of metal. As a result, the supporting shaft 5 tends to be swaged insufficiently and becomes more easily to drop off from the supporting member 2.
Therefore, there is a need for a treatment tool in which a supporting shaft for pivotably supporting a manipulation member does not easily come off from the treatment tool.